["Population and Development Review, Volume 48, Issue 1, Page 189-215, March 2022. ", "\nAbstract\nThe relationship between levels of social and economic inequality and demographic changes remains poorly documented, particularly for fertility. Covering a period from 1986 to 2018, this paper documents a positive country‐level association between income inequality and the dispersion of first birth schedules among women from 88 countries of the Global South. This association is driven by a dual dynamic of the decreasing mean age at first birth among a shrinking group of women who transition to motherhood early, and the increasing mean age at first birth and rising heterogeneity in the timing of childbearing among a group of first birth delayers. We show that this association is strongest in countries where the total fertility rate is below 2.5 children per woman. We argue that differential opportunities for accessing quality education, formal labor markets, and migration are potential drivers of the rising heterogeneity in the ages at which women transition to childbearing. These results highlight the importance of examining societal and demographic processes jointly and clearly indicate that more and better‐quality data on social and economic inequality are needed.\n"]